Re: [HCDX] Dxers Unlimited weekend edition for 7-8 July

["Prof. Arnaldo Coro Antich" <inforhc@xxxxxxx>]

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for  7-8 July 2007
By Arnie Coro
radio amateur CO2KK

Hi amigos radioaficionados around the world and those in space now 
too... Welcome to the weekend edition of your favorite radio hobby 
program coming to you via short wave and also on the world wide web 
streaming audio feed from 05 to 07 hours UTC. I am Arnaldo, Arnie, Coro, 
radio amateur CO2KK and as always it's my pleasure to share with you 
about seventeen minutes of on the air and on the web time...

Here is now item one: The latest solar cycle 24 forecast now available 
from several well known scientific institutions ,  are placing the start 
up of the climbing phase of the cycle  due to be starting during the 
second half of 2008, so, be aware that for the next year  or even 
longer, high frequency bands propagation will be limited to the lower 
bands...In other words we are going to see very few if any band openings 
via the F2 layer on the
bands between 20 and 30 megaHertz amigos !!!

Item two: Closely related to our first item of this program,,, our 
popular ANTENNAS section of Dxers Unlimited, will tell you how a rather 
nice and easy to build antenna for the 80, 40 and 15 meter bands can be 
made with just two loading coils and the information provided 
here...It's a rather compact wire antenna by all standards, but it will 
put you in the capacity to operate on two low frequency amateur bands, 
PLUS as a bonus, the antenna works quite nicely also on the 15 meters 
band, so you can monitor the 21 megaHertz ham radio band for openings 
that eventually may happen when sporadic E layer propagation is 
present...and in the rare opportunities when the F2 layer propagation 
will open up above 20 megaHertz.



Item three: Providing reverse polarity protection to all equipment that 
you may own and that can be powered from an external power source is 
something that is very easy to implement, and can save you a lot of 
headaches...and a lot of money too.

In a few seconds more about compact antennas for the low ebb of the 
solar cycle, and later reverse polarity protection for equipment that is 
powered from  external power supplies....

Stay tuned, I'll be back in just in few seconds after a brief interval..

.....


You are listening to Radio Havana Cuba, the name of the show is Dxers 
Unlimited, and sure, you can get in touch with me to send your radio 
hobby related questions, signal reports and comments about the program. 
Send mail to arnie@xxxxxx, or VIA AIR MAIL to Arnie Coro, Radio Havana 
Cuba, Havana, Cuba...

Now here is ,once again as requested by many Dxers Unlimited's 
listeners, as promised at the start up of the show, information about 
the KK-80-40 compact wire dipole antenna system, that has become very 
popular among Cuban radio amateurs, because it allows you to go on the 
air on the 80 meters band that is going to be in very good shape during 
the upcoming two winters as well as the spring and autoumn equinoctial 
DX seasons. The antenna also works very well on 40 meters where it is a 
full size dipole, and on 15 meters , using a simple antenna tuner, you 
will enjoy the benefits of a three half waves in phase center fed 
antenna that provides a little gain over a half wave dipole . Achieving 
this three band resonance is accomplished by means of the use of two 
long inductors , that is two coils that on 80 meters behave as end 
loading for the 40 meters antenna and when you operate on 40 or 15 
meters the same coils act as radio frequency chokes, effectively 
isolating the center section of the antenna from the end loading 
provided after the two coils.

The two coils are of course identical, and they are wound using number 
18 or 1.2 millimeters diameter copper enamelled wire... The coil forms 
are lengths of heavy wall PVC pipe of one inch or 25 millimeters , and 
to which you wind 30 centimeters of close wound turns.

In other words, you will be making two coils that have an inductance of 
approximately 120 microhenries.

Because their length to diameter ratio , these coils perform the dual 
functions of acting as end loading coils for the 40 meters band dipole 
to make it resonate on a segment of the 80 meters band, and when you 
feed the antenna with 40 meters band radio frequency energy, the coils 
act as radio frequency chokes, effectively isolating the 40 meters 
dipole from the end loading sections...

If you want to learn more about my compact KK-80-40-15 end loaded dipole 
antenna, just send an e-mail to arnie@xxxxxx, again, arnie@xxxxxx, or 
VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.

The step by step , easy to follow instructions for making this antenna 
have been used by many Cuban radio amateurs to build their three 
banders, that have allowed them to start working on 80 meters using an 
antenna with the footprint half the size of a standard 80 meters band 
half wave dipole, that will fit exactly where a standard 40 meters band 
half wave dipole is installed, and according to the results obtained, 
the relative loss of this antenna against the full size version is about 
half of an S unit or even less !!!
......

Si amigos, short wave listening is a low cost hobby, you can start 
enjoying it with a low cost portable receiver, but then you won't be 
able to have all the fun... You will want to buy or build a better 
receiver , and of course, install a nice external antenna...

Homebrewing short wave receivers is a lot of fun, but it does require 
that you learn quite a few things about electronics... but with the help 
of a more experienced radio enthusiast you can build your first homebrew 
radio and start picking up far away stations with it... One of the 
simplest and most effective receiver circuits that can be assembled at 
home using simple tools and a soldering iron is the CASCODE 
REGENERATIVE, closely followed by the HARTLEY regenerative detector , 
both using easy to work with vacuum tubes, that don't require a 
magnifying glass to see the parts !!

But if you prefer solid state , then there is the very easy to build and 
sensitive regenerative designed by radio amateur NA5N, who named it the 
Dessert Rat. You can find lots of circuit diagrams about regenerative 
radios by running a search engine scan under the words REGENERATIVE 
RADIO RECEIVERS....  I am sure that you will be simply amazed by the 
tremendous amount of information available via Internet about those 
fantastic receivers...

And of course, that you are kindly invited to request my own compilation 
of Regenerative Receiver Circuits, a dot zip file full of really 
interesting circuits, all tested by yours truly at one time or another....

......

Have you ever seen a damaged radio, tape recorder, walkman or any other 
piece of electronics that can be fed power from an external source ?
Well I have seen many , and have also attempted to repair the damages 
sustained due to the terrible impact of feeding the equipment with 
reverse polarity current.

Sometimes the radio, tape recorder or other device can be repaired , but 
some other times, any attempt to repair the radio is fruitless. Well, 
let me add that as a matter of fact, with a lot of patience and the 
typical  Cuban ingenuity I have repaired several radios and amateur 
transceivers of VHF walkie talkies that were considered to be a total 
loss...
But amigos, the best thing to do is to install reverse polarity 
protection to all of your solid state equipment...

It can be done in several forms... the simplest of them all is to 
connect a silicon diode of adequate current rating in series with the 
positive terminal of your equipment.

You can do it in a much better way by using a bridge rectifier for reverse
polarity protection, a zener diode for overvoltageprotection and you may 
want to add also a Metal Oxide Varistor or M O V, a semiconductor device 
that provides transient protection to your equipment.

If you want to be a perfectionist , then adding a radio frequency choke 
coil and several disk ceramic capacitors will further protect your 
equipment against radio frequency currents that may enter by way of the 
external power supply connection.

If you look at the price of your radio receiver, and the price of the 
components used to protect it, you will realize that the ratio of 
protected to protection is very much in your favor, in other words, with 
just a few dollars and maybe a half hour or an hour work, you can be 
sure that your valuable solid state equipment will be fully protected 
against reverse polarity , overvoltage of a permanent nature and voltage 
spikes, as well as achieving isolation from radio frequency currents too...

You wil also find out that most portable radios, handie talkies and 
similar compact equipment will always have a small area inside where the 
additional protection devices may be easily fitted....AND in case you 
don't have enough space for all of them, give always the priority to the 
reverse polarity protection diode amigos !!!

A fifty cent electronic component can save a radio receiver costing 
hundreds of dollars in case you make the mistake of connecting the 
external power supply with the wrong polarity !!!
....
This is Radio Havana Cuba, we are now using our new East Coast of North 
America high gain curtain array on 6060 kiloHertz from zero zero hours 
UTC in Spanish, a broadcast that ends at zero five hours UTC. At that 
time the 6060 kiloHertz 100 kiloWatt transmitter is fed with our English 
language program until zero seven hours UTC ....So , if you want to 
practice your Spanish, be aware that a nice signal is avaialable all 
along the East Coast of North America from 8 PM daylight savings time 
until one o'clock in the morning EST.

Now let's take a quick walk to Arnie's workshop, where yet another nice 
and rather unusual regenerative receiver project is under test. The 
unusual thing about this circuit arrangement is that it uses two standard
radio frequency type pentodes , one acting as a regenerative detector 
and the other one as an audio amplifier stage. The unsual thing about 
this radio is that the two vacuum tubes operate with very low plate and 
screen grid voltages, between 12 and 24 volts, so they can be fed from a 
standard easily built and very safe to handle solid state power 
supply.Si amigos, radio is an experimental hobby , and experimenting 
with radios is something really fascinating !!!

And now before going QRT here at Dxers Unlimited's weekend edition, here 
is Arnie Coro's HF plus low band VHF propagation update and forecast...

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